frightened and alarmed at the unusual sight of an enraged polar bear rushing in their direction, bill and tom had turned and fled at the first appearance of danger. they were not cowards, and would probably have faced a mad bull, but that was something they were used to, while a bear was something new.

so they raced back over the ice toward the place where the disabled airship rested.

"quick!" yelled bill.

"they'll all be killed!" cried tom.

"who?" asked the professor, dropping his tools.

rapidly the two helpers told what had occurred, and how they had left andy and the boys as the bear was rushing at them, the hunter having no more cartridges in his gun.

"take two rifles from the chest!" exclaimed the inventor. "washington and i will follow as soon as we get our furs on! hurry now!"

tom and bill needed no second bidding. seeing that the magazines of the rifles they took were filled, they hastened again over the ice and snow in the direction of sudds and the boys. as they hustled along, the sun, which had been hidden by clouds, emerged and shone with dazzling splendor on the ice fields. it almost blinded the men.

as they ran on they heard a shout behind them. turning, they saw washington and the professor, each with a gun, following. they waited for the pair to come up.

"how far away is the place?" asked mr. henderson.

"we must be close to it now," said bill. "yes, there is the bear andy killed," pointing to where the dead animal was stretched on the ice. "but where are the boys?"

"and where is andy?" asked amos henderson.

not knowing what had become of the hunter and the boys, the rescue party was puzzled. they looked on every side but saw no traces. the ground was so uneven that the professor suggested the hunter and boys might be lying wounded in a hollow, and screened from sight.

"we must scatter and look for them," he said.

meanwhile the three in the ice cave had been looking about them. they saw what had brought them into the place. it was a big cavern hollowed out by nature in the frozen crystals, and leading to it was a smooth inclined plane of ice.

"how are we going to get out?" asked jack, after all three had taken a survey of the cavern.

"can't we walk up the place where we slid down?" asked mark.

jack was already busy trying to climb up the slippery place. it was much harder than it seemed. the incline was a glare of ice, and jack's first attempt sent him sliding back with considerable force to the cavern floor.

"there's only one way to do it," said andy. "you must take my hunting knife and cut steps in the slide. then you will have some support for your feet."

the boys saw this was good advice and followed it. but the ice was frozen almost as hard as stone, and after chipping and cutting away for half an hour they only had three niches.

"at this rate we will have to stay here several days," said the old hunter, and there came an anxious note in his voice. "i wish we could send word to some of the others."

"hark! what was that?" asked jack suddenly.

all listened. there came a faint report, like that of a gun.

"it's the professor, washington, and the two farmers searching for us!" exclaimed mark. "they are firing their rifles."

"that's it! they can't find us because we are down in this hole," said

andy. "if i only had a cartridge now i could give an answer."

there came another report. this time there was no doubt that signal guns were being fired, for the shot sounded quite close.

jack put his hand in his pocket. his fingers touched something.

"hurrah!" he cried. "i have my revolver and there are four shots left!"

he passed it over to andy, who shot twice at intervals of about a quarter of a minute.

"where are you?" they heard a faint voice calling from somewhere above their heads.

in reply andy fired the last shot. it was responded to, and then, a few seconds later, a dark object loomed up at the opening at the top of the inclined plane. the prisoners, looking up, recognized the professor.

"hello, down there!" he shouted.

"hello, up there!" answered andy.

"we'll get you out!" called down the inventor. "how did you get there?

what do you need in order to come up here?"

"we slid down," said the hunter in reply, "and we didn't do it for fun either. if you're going to get us out you'll need a long rope."

the professor, sizing up the situation, sent bill jones back to the ship on the run to bring a long stout cable. while this was coming there were questions and answers sent up and down the inclined shaft that told each of the two parties what had happened. in a short time the rope was brought, and one end fastened to an iron bar thrust into the ice, while the other was thrown down to the prisoners. with this as an aid and guide they were able to walk up the incline and soon were on the surface again.

"there, i forgot something!" exclaimed the old hunter as he emerged from the mouth of the shaft.

"what?" asked the professor.

"the polar bear," was the answer. "i think i'll go back after him. the skin may be valuable."

"there are plenty more," said the inventor. "we have no time to go back after this one. i must hurry to the ship."

pulling up the rope, and strapping their rifles on their backs, the party of rescued ones and rescuers began their march to the airship. they decided to leave the bear andy had first shot on the ice, and come back later for some steaks.

it was a bright day, and though it was very cold, being about twenty degrees below zero, there was no wind, which was a great relief. the party marched on, with andy in the lead. he had reloaded his rifle with some ammunition the helpers had brought from the ship, and he was almost wishing he would meet another bear or two, now that he was ready for them.

just as the adventurers turned around the side of a large ice hill, which hid the airship from their sight, they heard a queer noise.

"what's that?" asked the professor.

"sounded like some beast roaring," answered jack.

"look out!" shouted andy, springing back, and bringing his gun to bear.

"we're in for it now!"

"sea lions, by their looks!" exclaimed the inventor. "a whole crowd of them and they are right between us and the ship!"

the next instant the party came into full view of the beasts. there were about two hundred of them, great big brutes, with sharp tusks. at the sight of the men and boys the animals set up a chorus of roars that sounded as if several score of real african jungle lions had broken loose. at the same time the beasts, with curious hitchings of their unwieldly bodies, advanced on the adventurers!

"get your guns ready," cried andy. "these fellows mean business! make every shot tell!"

he had already begun firing and two of the sea lions toppled over in quick succession, testifying to his good aim. then the boys, the two helpers, the professor and washington began a fusillade that made the icy regions echo and re-echo as though a battle was in progress.

but the number killed among them, and the sound of the guns, did not halt the progress of the beasts. on and on they came, their roars increasing in fierceness.

the continuous firing could not be kept up long. already the old hunter's gun was empty, and there was no spare ammunition now. one after another the rifles of the others were emptied of their cartridges. still the beasts came on.

"we must retreat!" shouted andy. "back to the ice cave! they can not get us there!"

"but what about the airship! we must regain that at any cost!" called the professor.

"wait until these beasts go away!" yelled andy. "if they get us down it's only a matter of seconds before they'll kill us with those tusks! run back!"

all turned to execute this command. there was only a narrow opening in the slowly encircling ring of sea lions, and this the adventurers made for, running toward the ice cave. they had passed beyond the mass of the beasts, when a loud cry from jack startled them. at the same time he pointed ahead.

there, coming on at full speed was a pack of polar bears! the adventurers were between the two forces of enraged animals!